FS smoke agent is used by the military to hide tanks and troops from the enemy. FS smoke agent is currently being stored in metal containers which are deteriorating. Visual inspection will show that the FS smoke agent is a viscous black fuming liquid when it is contaminated with corrosion. There exists, therefore, an urgent requirement for the development of an ecologically safe method for demilitarization of the bulk FM smoke agent.
FS smoke agent is a non-combustible screening smoke consisting of a mixture of sulfur trioxide, SO.sub.3, in and chlorosulfonic acid, CLSO.sub.3 H. The standard solution of FS smoke agent for military use consists of 55 percent sulfur trioxide and 45 percent chlorosulfonic acid by weight. Liquid FS smoke agent has a density of 1.9, about the same as sulfur trioxide, and it decomposes when heated to 80.degree. C. (176.degree. F.). When exposed to moist air, the agent reacts vigorously with the moisture, decomposing into aqueous hydrochloric acid, HCL(l), and sulfuric acid, H.sub.2 SO.sub.4 (l). Contact of liquid agent with skin can cause severe chemical burns. FS smoke vapor causes irritation of the throat and eyes, a feeling of constriction around the chest, and a prickling sensation on the skin.
Sulfur trioxide is a planar, triagonal, and symmetrical molecule in which the three S--O bonds are exactly alike. These bonds are resonance hybrids with one and one-half bonds each. Upon hydration, amination, or hydrochlorination, sulfur trioxide converts from a planar structure to products with near-tetrahedral bonding structures. Chlorosulfonic acid, CLSO.sub.3 H, has a similar molecular structure; a tetrahedron with one of the OH groups now replaced with CL. Liquid sulfur trioxide and chlorosulfonic acid have boiling points of 44.8.degree. C. (112.6.degree. F.) and 158.degree. C. (316.4.degree. F.) respectively, but FS smoke agent decomposes at a temperature of 80.degree. C. (176.degree. F.). This behavior of the agent indicates that the mixture of sulfur trioxide and chlorosulfonic acid is not a simple solution, but rather that the mixture has a stable bonded structure, either by complexation or by weak covalent bonding.
FS smoke agent is a liquid at room temperature. When pure, the solution is a viscous pale yellow fluid with a strong acrid odor. Dry FS smoke agent is stable when stored in metal containers; however, the agent vigorously corrodes metals in the presence of even very minute amounts of moisture. When in contact with water, FS smoke agent reacts violently, generating large amounts of heat. Although it is not combustible itself, it can be a fire hazard in the presence of other materials which are combustible.
When FS smoke agent is atomized in the air, the sulfur trioxide quickly evaporates from the droplets of agent, and reacts with moisture in the air to form sulfuric acid vapor. The sulfuric acid vapor condenses to produce smoke particles. Water vapor in the air is the primary factor affecting the evaporation of sulfur trioxide from FS smoke agent. The absorbtion of moisture by FS smoke agent generates heat, and the heat causes the sulfur trioxide to evaporate further. The water vapor concentration in the air, therefore, determines the rate of evaporation and the total quantity of sulfur trioxide being evaporated.
Based on the facts presented here, it may be concluded that FS smoke agent does not manifest the characteristic behavior of either of its component compounds, and that it must be considered as a unique chemical mixture. For the above reasons conventional disposal methods are inadequate and unsafe in the disposal of FS smoke agent.